In the information-oriented society in recent years, the amount of data to be stored in a recording medium is continually increasing. For this reason, a recording apparatus and a recording medium with an outstandingly high recording capacity have been desired. Also, hard disks, which are currently in an increasing demand as an economical recording medium of high capacity, are expected to be required to have recording density of one terabit or more per square inch, which is ten times the current density, in coming years.
In a magnetic recording medium used in conventional hard disks, a predetermined region of a thin film including polycrystals of magnetic fine particles is used as one bit for recording. In order to increase recording capacity of a magnetic recording medium, the recording density should be increased. In other words, it is necessary to reduce the recording mark size which is usable for recording of one bit. However, when the recording mark size is simply reduced, the influence of noise which depends on the shapes of magnetic fine particles becomes nonnegligible. If the particle size of magnetic fine particles is reduced to lower the noise, a problem of thermal fluctuation occurs, which makes it impossible to maintain recorded data at a room temperature.
In order to avoid these problems, a bit-patterned medium (BPM) has been proposed, in which the recording material is separated by a nonmagnetic material in advance, and a single magnetic dot is used as a single recording cell to perform read and write.
In magnetic recording media installed in HDDs, there is an arising problem of the interference between adjacent tracks which inhibits improvement in track density. Particularly, reducing a fringe effect of a write head field is a significant technical problem to be solved. To solve this problem, there has been developed a discrete track recording-type patterned medium (DTR medium), in which the magnetic recording layer is processed so that the recording tracks are physically separated from each other. In the DTR medium, it is possible to reduce side erase which erases information in the adjacent tracks in writing and side read which reads information in the adjacent tracks in reading. On this account, the DTR medium is promising as a magnetic recording medium capable of providing a high recording density. Incidentally, it should be noted that the term “patterned medium” as used herein in a broad sense includes the bit-patterned medium and DTR medium.
In the manufacture of a patterned medium (DTR medium or BPM), it is an extremely significant problem to reduce irregularity on the surface of the medium, from the viewpoint of flying property of the head. In an ordinary patterned medium, magnetism is separated by using a method such as etching to physically separate the magnetic recording layer. However, if a magnetic recording layer having a thickness of several tens of nanometers is completely etched, the flying property of the head is deteriorated, and as a result, the HDD does not properly function. To overcome this problem, a method of filling recesses is well known. Also effective is a method of deactivating recessed regions as we suggest. In this method, regions of the magnetic recording layer corresponding to the non-recording regions in a patterned medium are deactivated to lose the magnetism thereof, and as a result, a separating effect can be obtained without physically separating the magnetic recording layer.
Japanese Patent No. 4191096 discloses a method of manufacturing a magnetic recording medium including cleaning a magnetic recording layer by means of non-oxide-type gas which contains hydrogen after the removal of a mask in order to prevent the magnetic recording layer from deterioration or corrosion caused by etching which uses an oxidizing gas. In this method, the cleaning step is introduced only for focusing on the affect caused by the reaction between a magnetic recording layer and an etching gas, while the affects between mask layers or between a mask layer and an etching gas are not taken into consideration.
Japanese Patent No. 4128509 discloses a method of manufacturing a magnetic recording medium which uses two mask layers. The patent discloses that a combination of a mask layer including Si and a mask layer including C may be selected as the two mask layers. However, there is no disclosure of the problem caused by such a combination nor countermeasure therefor. Particularly, steps of cleaning or removing unnecessary components as disclosed in Japanese Patent No. 4191096 are not disclosed in Japanese Patent No. 4128509.